I'm going for the live nirvana tone. I know that Cobain used a mesa boogie studio .22 preamp, but that isn't manufactured anymore, so can someone help me, what a similiar sounding amp would be?
I remember reading somewhere that he had that preamp going into some kind of PA power amp into a 4x12 but I am sure Nirvana site would be better suited at answering that question.

I'd say something like a Roland Jazz Chorus (or one of the big Fender tube blues amps like a Blues Deluxe (Custom Twin, etc.) and some pedals might be a good place to start. The JC-120 can do the cleans as can the Fender, for the distortion sounds you could possibly try one of the Mesa Mark simulations as the distorted sounds seem to be the mid channel on a Mesa Mark amp. Maybe something like the Jekyll & Hyde overdrive/distortion pedal. I'm basing this on analysis on a song like "Nevermind".
diabolical I also thought, that is should buy a mesa mark simulation, but live he used the mesa boogie preamp for clean parts also, and he got the distorted sound with boss distortion pedals, and since I've already got a ds-2, I would like to use that as a distortion.
I can't give you a precise answer. Currently most of the time for bedroom practice, sometimes live, but I know that I am going to use it a lot live.
A touch of spring reverb would help for the cleans. TBH, I think you can do really well with Mesa Mark V as well, as it has those sounds you hear on the record, or maybe even the Mesa Express 50 watt combo, so you won't need distortion pedals. It's not the cheap route, but probably best sounding.
Get any Mesa that has a decent heavy tone - use the amp distortion - you will sound great. A Mark V is overkill, you could easily get by with an Express combo or Roadster or Rectoverb combos, which are much cheaper. You don't need the ds2 or ds1 at all - use the amp's distortion - it'll sound better. Those pedals are terrible and the only reason they even sounded half decent when used by Kurt or Satriani is because they were running them in cranked 100 Watt 4x12 Marshall Stacks. Every Mesa amp has great switching options, so a pedal won't be necessary. Get a chorus Pedal - the Electro-Harmonix one is what he used I think, but any will do. Don't get a Fender amp if you can Afford a Mesa - it's just way better suited for heavier music. I used to run a Ds1 into my old Fender HRD 2x12 - it sounded terrible and nothing like Nirvana.
Don't get a Fender amp if you can Afford a Mesa - it's just way better suited for heavier music.

As a Fender HRD owner currently looking at Mesas & Oranges to play heavier music through, I agree with this 100%
Sturgeon's 2nd Law, a.k.a. Sturgeon's Revelation: “Ninety percent of everything is crap.”

Why, yes, I am a lawyer- thanks for asking!

Log off and play yer guitar!

Strap on, tune up, rock out!